Channel estimation for DS-CDMA with aperiodic spreading codes

For high performance CDMA communications, multiuser detection is often required to suppress the multiple access interference (MAI). Most multiuser detectors rely on accurate channel information to recover the multiuser digital signals. This paper studies the blind channel estimation problem for DS-CDMA systems using aperiodic spreading codes. The Maximum Likelihood (ML) estimator is formulated for channel estimation. We first convert the multiuser parameter estimation problem into a set of single user optimization problems via alternating optimization, and then determine the channel parameters for each user using an iterative algorithm derived. It is shown by computer simulation that this iterative algorithm can reach global maxima almost always under medium SNR values.